they are different alphabets!! like a, b, c, d; to be precise, consonants. they are pronounced differently take e.g. ghar -home i go to home - main ghar jaata hoon if u pronounce it 'gar', entire meaning would change i will be -"if i go(it will be sounding a like of urdu poetry)", ofcourse it is understandable, but only if the context is known u say pal instead of phal, again u are saying something totaly different. pal- moment phal - fruit. I can put more such type of examples. In Urdu, according to the book i read to learn it, writer called them 'heavy sounds'. because u have to pronounce ha in the end. so simple k + ha = kha. for example in chemistry, calm, it is simple 'k', but in english accent i have heard it manys time that they say 'come' like 'kham' (there is k is like kh sound as well). better u listen to them (in google translate), they are different alphabets, should be pronounced distinctly. and practice, they are not so hard. :)