I don't know of any websites either, but I can recommend two terrific books. Reuben Fines' little gem from 1943 is titled The Ideas Behind The Chess Openings. Make sure you get it in algebraic and realize that many of today's popular openings are simply not covered. Paul van der Sterren's Fundamental Chess Openings is today's gold standard for one volume opening books. He doesn't go deep (that's what DBs are for), but he'll take a paragraph to explain a single move. Highly recommended! Oh, and not just by me...LOL
Ideas behind openings


Chess experts advice... Choose the opennings that fit your playing style. )... If you have already the such one.

Example: Italian game. White wants d4 and e4 pawns. So white often plays c3 and d4. Knight b to d2, heading to g3.
IME getting into the theory of various openings hasn't worked too well for me so far. I've only been here for four months and have been stuck between around 820 & 850 for the last two. Prior to that at one point I was at 897 and could sometimes beat players with higher ratings. Up to that point my opening consisted of pawn to d or e4, develop as fast as possible and act or react as the situation justified.
After the first two months i got interested in the various specific openings and have been trying them with limited success for the past two months I dropped below 850 fast. In my case and maybe overall at this level focusing on the structure of an opening can lead to blunders and can be a deterrent to adapting offensively or defensively to what the opponent's doing.

Chess Openings Resources for Beginners and Beyond...
https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond
Thanks RussBell, that looks like it has HEAPS of stuff! I will bookmark that and keep coming back to it.
Ipswich Matt, no not really any opening at the moment, so far I've experimented a bit with the London and Jobava London. Think I'd like to try a couple of e4 openings too. But not really any ideas yet about one to settle on. As most people seem to say, probably not worth getting too into any opening at this stage, until I stop the constant blunders.... I just feel it's nice to have a general idea of what you're trying to do at the start of each game.

I often see people recommending to beginners not to worry about memorising all the lines of an opening, but instead to learn the main ideas / goals of an opening. This makes sense to me. But I haven't yet come across any particularly good resources at explaining the main ideas of openings.
Can anyone recommend any good websites that explain in plain English what the main ideas and goals are for particular openings?
In "general" The idea of any opening is to accomplish the following:
1. Fight for control of the center.
2. Place your pieces on active squares.
3. Develop a middle game plan.

I often see people recommending to beginners not to worry about memorising all the lines of an opening, but instead to learn the main ideas / goals of an opening. This makes sense to me. But I haven't yet come across any particularly good resources at explaining the main ideas of openings.
Can anyone recommend any good websites that explain in plain English what the main ideas and goals are for particular openings?
In "general" The idea of any opening is to accomplish the following:
1. Fight for control of the center.
2. Place your pieces on active squares.
3. Develop a middle game plan.
The third point always frustrates me.
These high level Chess strategies are puzzle for me.
I always try to figure out what to do after... when the first development of the pieces is completed ?

I often see people recommending to beginners not to worry about memorising all the lines of an opening, but instead to learn the main ideas / goals of an opening. This makes sense to me. But I haven't yet come across any particularly good resources at explaining the main ideas of openings.
Can anyone recommend any good websites that explain in plain English what the main ideas and goals are for particular openings?
In "general" The idea of any opening is to accomplish the following:
1. Fight for control of the center.
2. Place your pieces on active squares.
3. Develop a middle game plan.
The third point always frustrates me.
These high level Chess strategies are puzzle for me.
I always try to figure out what to do after... when the first development of the pieces is completed ?
Yep...the first 2 are easy. Its when you get to the middle game planning part that the game truly begins.
There are 2 ways to do this. One is easy, one involves a bit more effort.
The easy way:
Scan the opponents 5th. and 6th. ranks (3rd. and 4th. if they are white). Look for any weak pawns, and or weak squares. The closer to the center, the better. Those are your targets to attack.
If you want to put in more effort, and learn more:
Middlegame Planning.
1. Expand your position:
a. Gain more space.
b. Improve the position of your pieces.
2. Decide on what side of the board to play.
a. Queenside: a-c files.
b. Center: d-e files.
c. Kingside: f-h files.
Compare, space, material, and weakness(es)
3. DO NOT HURRY. Regroup your pieces, and be patient.
I often see people recommending to beginners not to worry about memorising all the lines of an opening, but instead to learn the main ideas / goals of an opening. This makes sense to me. But I haven't yet come across any particularly good resources at explaining the main ideas of openings.
Can anyone recommend any good websites that explain in plain English what the main ideas and goals are for particular openings?