present participle和infinitive verb的区别

infinitive verb often plays a role of a subject,an object,an attribute,a predicative,an adverbial modifier and a complement,and it often means "the things will be done",for example:Please get me something to eat.It's impossible (for us) to live without water.
the usage of present participle is almost the same,but the only thing differs from each other is that an infinitive verb emphasizes something will happen in the future,but a present participle suggests something is in progress.For example,a flying bird,a boiling kattle.
the structure of Present Continuous Tense is "am/is/are + doing",the "doing" here is one of the important part of the tense,and it means nothing without the link verb in front,for example,"I'm running." and "A running car"