The dword ptr part is called a size directive. This page explains them, but it wasn't possible to direct-link to the correct section.
Basically, it means "the size of the target operand is 32 bits", so this will bitwise-AND the 32-bit value at the address computed by taking the contents of the ebp register and subtracting four with 0.
It is a 32bit declaration. If you type at the top of an assembly file the statement [bits 32], then you don't need to type DWORD PTR. So for example:
[bits 32]
.
.
and [ebp-4], 0
Consider the figure enclosed in this other question.
ebp-4 is your first local variable and, seen as a dword pointer, it is the address of a 32 bit integer that has to be cleared.
Maybe your source starts with
Object x = null;
Source: Stackoverflow.com