Your actions

Fold means leave this hand and give up your claim to the pot. Check means pass the action without betting, and is legal only when you owe no chips to match the current bet.

Bet puts chips in when no one has yet bet on that street. Call matches the amount you face, limited by your remaining stack. Raise increases the current bet.

A raise to 20 means your total contribution on this street becomes 20. A raise by 20 means adding 20 to the previous bet total. Always confirm which amount is displayed.