to do 和doing :
to do 是动词不定式,非谓语动词,用在固定短语的情况比较多,例如,tell sb.to do sth.等.
doing,是现在分词,也叫动名词.用在固定短语的情况也是比较多的.例如,Thank you for doing,the reading room,look forward to doing,get used to doing 等等.用法很多,简单介绍一下,希望你能用得上.