5 minutes means you have 5 minutes to make all your moves. If you see for example 5/5 or 10/5 the first number is the time you have to complete the game, the second number is increment in seconds, which is added to your clock after each move you make. So 5/5 is 5 minutes for all your moves plus an extra 5 seconds each time you move. The other option is daily chess where you can select 1, 3, 5, 7 or 14 days to make a single move. In daily chess you may also use the analysis board to play some moves, predict your opponents reply and try out ideas for the game in progress.
How do the timers work?
Hi Strangemover, tks so much for your reply. As a newbie to both the site & the game am I being naive to think I could have a game with another player of similar abilities in real time where we each play out our move until the game is over? I don’t think I want a game where we each make a move a day. What would you suggest my settings should be to start a game online with an appropriate opponent? ( and what exactly do the settings you suggest mean? )

Your settings are automatically set to search for an opponent with a rating between 200 above and 200 below your own I believe. If you wish you can change this but that range should be ok to find an opponent with similar ability. However, as you are new and have not played many games it takes a while for your rating to stabilise and become accurate so you may have some games vs players of a different level. There's not much to be done about that really. As for what sort of game you play it's entirely up to you and how much time you have. It's better for a beginner to play longer games so there is time to think a bit more carefully so maybe 30/0. 30 minutes for each player to complete the game. Bear in mind though that if you both use all that time the whole game may take up to an hour.

Hi Jeannie!
Sorry to hear about your game! I am going to attach a few links to some very helpful articles regarding time. Most were very well explained by Strangemover! Now, keep in mind that you can change you settings to suit your needs. You simply go to Settings---> and check out the different customizable options you have!
Here are the time articles:
https://support.chess.com/customer/en/portal/articles/1444850-how-do-the-time-controls-work-in-the-live-chess-?b_id=12321
https://support.chess.com/customer/portal/articles/1444851
Here is where I found this information. If you happen to get stuck on something you don't quite understand you can always search a question or a "keyword" and it will pop up several articles!
https://support.chess.com/customer/portal/articles/1444851
I hope this helps. If you need further assistance, you have your Chess.com community and staff to help! Have a good one-
Hi, just played first online game ever as a total beginner. Assumed 5 mins meant we had to make our move within 5 mins - so I chose this. After a couple of moves each, my opponent made a move and I followed with my move after about 10 seconds only to be told I had lost as I had been timed out. Totally bewildered and very disappointed. Would really appreciate some help as I am enjoying playing with computer at level 2 but would really like to try playing another player who is at the same level as me but clearly need to understand what the settings mean. Thanks Jeannie