i read the ardor thread and it says basically ardor is a child chain of nxt?
Nxt is an assest exchanging blockchain platform but isn't ardor will function it similar like nxt?
No, Ardor is a complete new blockchain. It's like a "mother chain" where all other child chains keep their transaction hashes for consensus.
Ignis will be the first child chain for Ardor, with all the features that Nxt has now.
But Nxt will continue to exist, the core devs committed to keep support of Nxt up!