"Bebendo" is exactly what James has explained. It is related to verb "drink" + ING, which denotes gerund (something you are doing at that moment). ex 1: Ele está bebendo cerveja. (He is drinking beer.) ex 2: Estou bebendo uma xícara de café. (I am drinking a cup of coffee.) "Tomando" can have the same meaning of "bebendo" or you can also use it such as "take" + ING in English. ex 1: Estou tomando uma xícara de café. (I am drinking a cup of coffee.) ex 2: Estou tomando ônibus perto de casa. (I am taking the bus near home.) ex 3: Ela está tomando conta do meu filho. (She is taking care about my child.) That's it.

to have (a drink) e.g. I'll have a beer. (Eu tomo uma cerveja).

drinking