strstr and strchr

looks strange to me 
if i look for a str using strstr it gives me the starting index of the string. so let say if i'm looking for "firstName" in "<Info firstName=\"sam\" lastName=\"Smith\" />" using 
strstr(ptr, "firstName");  i would get the pointer pointing to the f in firstName.


whereas if i use strchr and using a slight variation of the string mentioned above(suing ' instead of ")  "<Info firstName='sam' lastName='Smith'/>" 
strchr(ptr, "'") returns a pointer pointing after the ' 
so a printf("[%s]\n", strchr(ptr, "'"));
would print [  lastName='Smith'/>]  

which doesn't make sense to me.

can someone shed some light. TIA !