What is the meaning of いる?

to exist, to be

to have

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.

1. Indicates a progressive or continuative tense: to be doing

   Indicates a progressive or continuative tense: to be doing

   Indicates a regular, repetitive action.

   Indicates a state resulting from the action.

   to sit

   Source: wiktionary.org