The verb dienen translates as "to serve." But like in English, there are many contexts for this verb that don't have to do with relationships between people. Very often, dienen is used to describe how something serves a certain purpose:

Sie dienen dazu, in Häusern böse Geister zu vertreiben.

They serve to drive evil spirits out of houses.

Caption 27, Cettina erklärt: Pfingsten

 Play Caption

Sie dienen vielen Tieren als Futter.

They serve as fodder for many animals.

Caption 50, Deutsch mit Eylin: Bäume

 Play Caption

banner PLACEHOLDER

The verb bedienen is related, but actually has a couple of different meanings. It can relate to waiting tables, though the actual act of serving food, whether at home or in a restaurant, is servieren. The reflexive verb sich bedienen means "to help oneself." Below, you'll see the formal and informal versions:

Dann bedienen Sie sich einfach. Komm! -Komm!

Then just help yourself. Come on! -Come on!

Caption 24, Großstadtrevier: Von Monstern und Mördern

 Play Caption

Viel Spaß! Da hinten steht was zu Trinken. Bedient euch. -Ja.

Have fun! There's stuff to drink back there. Help yourselves. -Yeah.

Caption 52, Die Pfefferkörner: Alles auf Anfang

 Play Caption

The noun die Selbstbedienung, a word that you might find at a café or gas station, means "self-service." But this doesn't necessarily mean you can help yourself!

An important meaning of bedienen is "to operate," as in to operate a device or machine. A user's manual is called die Bedienungsanleitung.

Wenn ihr diesen Wendehammer richtig bedient, könnt ihr die Mauer einreißen.

If you operate this turning area correctly, you can break down the wall.

Captions 73-74, Es war einmal … Entdecker und Erfinder: Archimedes

 Play Caption

Further Learning
You'll find many examples of these nouns and verbs used in context on German Yabla. Just do a quick search!