BVA is boundary value analysis...in this will check for
length of the fields like the field will not accept more
than max char length etc  and where as 

ECP is equivalent class partition ...will check for what are
all the valid and invalid classes like Name field should not
accept special chars etc...

Hellow,

BVA - Boundary value analysis 

When we have to validate a text field or any other field 
whether it is accepting the no of Characters as per the 
requirement or not,then we will go for BVA

In BVA, we will test the extream boundaries by taking 
max+1 ,min-1 values. If the field behaving correctly for 
these extream values then inbetween also works fine. 

ECP  - Equivalent class partician 

When we have to validate whether the field is accepting the 
correct data type as per the requirements or not we will go 
for ECP

In ECP , we will devide the data as 'Valid' and 'In valid'
Valid data - Integers , numericals ,alpha numericals 
Invalid data - Speacial charecters , blank 
We will apply both the types and check whether 
functionality works correctly or not

Thanks