Hi ujjwal.

Firstly, its good to know you applied for law.

and now coming over to your query, BLAT is the entrance test for the admission to BALLB course in Banaras Hindu University. BLAT is Banaras hindu university Law Admission Test. Whereas, BALLB is the integrated course of bachelor of arts and law , which is a 5 year degree. 

BLAT is the exam BHU conducts for the admission to the course of BALLB. 

Down here is the official exam information ,that you can read.

Banaras Hindu University will conduct BLAT 2018 on May 27, 2018.The BHU LLB Admission Test commonly called, BLAT is the entrance examination administered by the central university for admissions to undergraduate law programmes including BA LLB. Candidates appearing for BLAT 2018 will need to register and fill application form of BLAT 2018 that begun on January 20,2018. Candidates eligible for BLAT 2018 will be allowed to appear in BLAT in offline mode. The Banaras Hindu University offers as many as 60 seats in the five-year law programme.

For any further queries, feel free to revert back .i hope it helps you. and if you like the answer then kindly upvote.

goodluck.