HI,
Equivanence partition:we check any one value in between the
range. 
For EX: if a range is 10 to 50  (10-50).ten we have to check
any one value in between the range. for this we take  40.it
means it it a valid test case. for these there are three
testcases will be given.
BVA:
we check the boundry values. in same example 10 to 50 means
we have to check  b giving 10 and 50 .
here ther are four testcase will be  given.

Boundary value analysis(BAV)and Equvilence partition both 
are techniques in black box testing 
 BAV:in this technique we split the domin in to input 
clases of data along its boundaries and generate test cases 
for boundary values 
lowervalue + 1 , Upper +1 ,Lower -1 ,Upper -1,Lower,Upper

Equivalence partition:in this technique we take the domain  
value and split the range in to equivalent classes and 
generate the testcases for equivalent clases

let me u explain with an example:
think a login page two text boxes for userid and passwd
and there are some conditions given in SRS which should be 
satisfied like for suppose
username: min length=4
          max length=7
          alphanumeric
for this if u where to write BVA and ECP
then it is in this manner
BVA
min+1 valid
min-1 invalid
max+1 invalid
max-1 valid

ECP    
valid       invalid
0-9         special characters
a-z
A-Z
so simple in
BVA:we are testing the boundaries
ECP: we are dividing input values to be given into valid 
and invalid values    
hope u can try it for passwd