Phrasal Verbs are idiomatic expressions, combining verbs and prepositions to make new verbs whose meaning is often not obvious from the dictionary definitions of the individual words. They are widely used in both written and spoken English, and new ones are formed all the time as they are a flexible way of creating new terms.
A reference page of 2,570 current English Phrasal Verbs (also called multi-word verbs) with definitions and examples is here.
Phrasal Verbs beginning with I :
Iron out : Remove small problems or irregularities
The management team IRONED OUT the tax problems before they gave the project the OK.
Issue forth : Come out of a place
New initiatives ISSUE FORTH from the government on a daily basis.