Does the vertex buffer layout update after you change the buffer data

OpenGL OpenGL: Basic Coding
1

If I have a vertex buffer with a layout stored at index 0 and then change the buffer data and create a new layout at index 1, will the different buffer layouts hold different data?
I’m very new to OpenGL so if I said something stupid I’m sorry.

Edit: I meant the glVertexAttribPointer.

2

What is a “buffer layout?” Buffers store data. And, outside of a few specific circumstances, changes to the contents of a buffer’s storage are visible to commands issued after them, and changes to the contents of a buffer’s storage are not visible to commands issued before making those changes.