Participles are non-finite forms of a verb. They can fuction as adjectives, or be part of the verb phrase in a sentence.
Present Participle is the -ing form of a verb:
ex.1 They are painting the building. ( => "painting" is a present participle, in this sentence part of the verb phrase "are painting.")
ex.2 The police stopped all passing cars. ( => "passing" is a present participle, in this sentence functioning as an adjective for "cars." )
Past Participle is the -ed (or equivalent) form of a verb.
ex.3 Research has suggested that there is a direct relation between smoking and lung cancer. ( => "suggested" is a past participle, in this sentence part of the verb phrase.)
ex.4 He is a trusted doctor. ( => "terusted" is a past participle, in this sentence an edjective for "doctor".)
Present Participe form of a verb very much resembles the GERUND of that verb.
A very brief diferrence between present participles and gerunds is that:
Participles are half-way between verbs and ADJECTIVES.
Gerunds are half-way between verbs and NOUNS. (i.e. gerunds are -ing forms which function as a nound in a sentence)
ex.5 They are finding a new way to fight AIDS. => present participle
ex6 Finding a new way to fight AIDS is still in progress. => gerund