It is virtually impossible to come up with a set of rules for Bingo that will apply to every single online game that you play for the simple reason that payouts and rules can be different from online bingo site to other online bingo site. However, with that in mind, it is still possible to develop a general set of rules that you can use to get acquainted to the general game of Bingo, with research from the actual websites you plan to play at filling in the rest of the information that you need in order to be able to determine how the Bingo games work in detail at your website of choice.
The Bingo game starts with you buying cards on them, these cards being arranged in a five by five grid. The five by five grid represents five columns labeled B-I-N-G-O respectively and of course each column being five squares long. These Bingo cards are basically the ones that are used in each Bingo hall, so for the most part you can be confident of the fact that the card will be like the one described here.
Once all of the players have chosen their cards and are ready for the actual game to begin, the bingo caller starts drawing balls at random and then calling out the numbers on those balls. The balls will have a number preceded by a letter and if one of your cards (or more than one of your cards) happens to have the number and letter combination called out, then you mark it off as being a combination that you happen to have.
Depending on what the rules of the game are, once a person has a certain pattern of boxes marked off as having been called, they can yell out Bingo and once their pattern is verified as being true, they will end up winning the game. There are a number of box patterns that might be used on a Bingo card, but the most common patterns are a border box pattern (where all of the edge boxes need to be marked off before Bingo is achieved), an X box pattern (where an X needs to be made across both long diagonals) and of course just a simple row or column being completely marked off is something that is fairly common a victory condition as well.