The suffix"waalaa" frequently used in Hindi denotes various things with different kinds of words. colloquially, it is used chiefly in association with nouns,adjectives,adverbs and oblique form of infinitive. It is equivalent to English suffix "er"; the one who does that activity for example to help=madada karnaa and helper means madada karne waalaa/waali/waale. it is used to convery that something is about to/expected to happen for example about to come=aane waalaa/waali/waale , about to go =jaane waalaa/waali/waale, he is about to go next week= vah agle haphte jaane waalaa hai.  proprietorship, houseowner= makaan waalaa, wealthy=paise waalaa,shopkeeper=dukaan waalaa. I hope the explanation would be helpful for you.

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Thank you ! Now I understand very well )

depend on sentence where it use. 
if i say "yeh wala do " here "yeh wala" mean "this one"
if i say "sabzi wala" then here the person who sold vegetables (sabzi means vegetable )