[verb]Used as a 補助動詞(hojo dōshi), after a verb in the て(-te)conjunctive form. Note that ている(-te iru) colloquially shortens to てる(-teru), ていた(-te ita) colloquially shortens to てた(-teta), etc.
[verb]Indicates a progressive or continuative tense: to be doing
[verb]Indicates a regular, repetitive action.
[verb]Indicates a state resulting from the action.