StringTake

StringTake["string",n] gives a string containing the first n characters in "string". 

StringTake["string",-n] gives the last n characters in "string". 

StringTake["string",{n}] gives the nth character in "string". 

StringTake["string",{m,n}] gives characters m through n in "string". 

StringTake["string",{spec1,spec2,…}] gives a list of the substrings specified by the speci.

StringTake[{s1,s2,…},spec] gives the list of results for each of the si.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.