Participles

A participle is a word that presents an action as a property or state of something: writing, beaten, closed, etc. In English there are two types of participles: present participles, which are usually formed with the ending -ing (e.g. writing, doing, seeing), and past participles, which are usually formed with the endings -en or -ed (e.g. given, closed, written). In Esperanto, there are six types of participles.

Active Participles

The active participles describe the state of the person or thing doing the action:
skribanta - writing
skribinta - written
skribonta - going to write
skribanta knabo - a boy who is writing
skribinta knabo - a boy who wrote

Mi estis skribanta. - I was writing.
Ili estos skribantaj. - They will be writing.
Ŝi estis skribonta. - She was going to write.

With the -o ending, we present the person who performs the action:
skribanto - writer (one who writes, or is writing now)
skribinto - one who wrote
skribonto - one who is going to write

Participles can also be used as adverbs:
Skribante li pensis pri ŝi. - While writing, he thought about her.

Passive participles

The passive participles express a quality of the thing, which is affected by the action:
skribata - being written
skribita - been written
skribota - going to be written
skribata letero - a letter which is being written
skribita letero - a letter which has been written

La letero estas skribata de mi. - The letter is being written by me.
La letero estis skribata de ŝi. - The letter was being written by her.
La letero estis skribita de li. - The letter was written by him.

More detailed explanations

Read here.

Exercises

Level 1, Level 2, Level 3