How to understand the register window of ollydbg?

What does Z 1 DS 0023 32bit 0(FFFFFFFF) mean?

The Z 1 part means the zero flag is set. DS 0023 32bit 0(FFFFFFFF) means the segment register DS contains selector 0023, which is a 32-bit segment starting at 0, with length FFFFFFFF (+1). In other words, the segment spans the entire address space.

Z 1 has nothing to do with DS 0023 and 32 bit 0(FFFFFFFF). The column which Z belongs to is an abbreviated list of the flags register (the "older" flags, "newer" one are listed below), with the value of each flag at the right. DS stands for 'data segment', in fact the column it belongs to lists the segment register with their values. Finally, 32bit 0(FFFFFFFF) is the size of those registers and the interval of values allowed in them.

I don't have any experience with ollydbg, but I can tell you without a doubt that the Z stands for the zero flag and DS 0023 is the value in the DS (data segment) register. I don't know what the rest means exactly. I think it's information about the memory address at that segment.

You should look at that set of information as two columns of register/value pairs. The first column are the various status flags, the next for the segment registers.