Does that impact the load time?
Gzip or Deflate are HTTP compression modules which allow your browswer to download a websites data more quickly.
Here is a primer on it from Yahoo.
http://developer.yahoo.com/blogs/ydn/posts/2007/07/high_performanc_3/
Directly, yes, but not in any noticeable way in normal conditions; like, instead of 10 ms, it will take 15, or something. Where it can be relevant is under heavy load; with compression less bits travel through the wires, it can prevent congestion.