Every time I read articles on chess I see people who say that chess is now dominated by computers. For example if you look for a thread on the subject 'Fischer vs Carlsen' (just an example) you see people comment that if Fischer had access to computers he would have been better. Why? What do modern GM's do with computers?
Masters use computers as training tools. They allow a master to quickly check the viability of variations and understand why some moves are good or bad. Further, they afford searchable instant access to millions of positions and countless openings to the master.
In short, the computer is your sparring partner, second, and librarian, and who works for cheap.
All current chess players use computers to improve their game. This includes evaluating new positions in the opening resulting in better and deeper opening preparation. They also can set up a board and let the computer evaluate for hours to discover new lines that were previously too complicated to discover.
Also all chess players maintain huge databases of games, this they can search for games played by a specific player (particularly useful in matchplay) or search through historical games that contained a given position. Thus the use of computers is a vital tool to improve ones game especially when dealing with the "opening preparation".
An example of how new chess players are coming up - Hikaru Nakamura claims to have never read a single chess book and learnt completely off the computer.
Today, chess is dominated by computers, that's true because for the same calculating scale (ELO rating), we can compare ELO points of computers and ELO points of humans.
Moreover, best chess players use chess engines to analyze positions. For instance, Viswanathan Anand currently use Houdini for training.
Computers allow unusual endgames to be solved much more quickly than a human can, if the human can do it at all. In Kasparov vs the World, the game ended with a 25-move forced checkmate discovered by computer.
Kasparov has said that computer + Grandmaster analysis is vastly superior than either computer or Grandmaster alone. I believe there was a chess league for a while that allowed strong programmer + player to compete one another along with strong chess computers or players alone. The combined players usually won tournaments. That's because the strong players can sense when a computer move is perhaps not the best long term strategic plan, although in the short term it is tactically justified.