You'll notice a handful of entries have '(a)' - this is to indicate a difference in a masculine/feminine speaker, as, in Russian, some words change depending on whether the speaker is male or female.
For example,
Я занят (I'm busy) --> as said by a male speaker
Я занята (I'm busy) --> as said by a female speaker
The extra -а is simply part of the feminine form. You’ll often see this with past-tense verbs and short forms of adjectives. This change refers to the person speaking, not the person you are talking to. So, if you're a lady, just note the 'a' and remember to use it in certain phrases when refrencing yourself!
Additionally, note entries marked by 'formal' and 'informal' tags. Some words or phrases can be seen as rude depending on the context and who you're speaking to.
До свидания, for instance literally means 'until the next meeting' and is used in formal or polite settings - on the other side, пока is closer to a 'see ya' and is much more playful and casual.