what are these english terms meaning?

Question

introductory adverbial clause
introductory prepositional phrase
introductory participal phrase

Answer 1

Introductory just means that they clause/phrase appears at the beginning of the sentence.

If you need more information, first you need to find out and understand what adverbs, prepositions and participals are. Then, you need to find out and understand what a clause is and put that together with what you learned about adverbs, prepositions and participals.

Answer 2

introductory means the phrase comes first in each sentence.

for example, the first one would be an adverb clause at the start of the sentence--Because he was sick, Edward couldn't join his friends for a swim.

the second one would be a prepositional phrase--At the pond, i saw a white duck feeding on bread crumbs.

and the last one would be a participal phrase--Reading her interesting novel, Martha didn't realize that it was an hour past bedtime.