Learn Russian: Мы говорим о характере.

The preposition о (about) always makes the following noun take the Prepositional case. For most masculine nouns ending in a consonant, like характер, you form this case by adding an -е to the end, making it о характере.

Why is the word for about just о instead of об?

You use о before words that start with a consonant sound, like характере. You only switch to об before words starting with a vowel to make pronunciation smoother, for example: об Иване (about Ivan).

Can I use характер to talk about a character in a movie or book?

No, this is a common trap! In Russian, характер only refers to a person's personality or nature (like having a good or difficult character). If you want to talk about a fictional character in a story, you should use words like персонаж or герой.

Does говорим mean we talk or we are talking?

It can mean both! Russian does not have a separate continuous tense like English does. You use говорим whether you mean we talk in general or we are talking right at this very moment.