An opening pattern, or fuseki in the game of go (goe, igo, paduk, baduk, weiqi). It consists of plays on parallel hoshi, or 4-4 points, along with the 10-4 point between them.
Like here:
---------------------------------------
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . O . . . . . , . . . . . X . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . , . . . . . , . . . . . X . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . O . . . . . , . . . . . X . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
| . . . . . . . . . . . . . . . . . . . |
---------------------------------------
The X's form the san-ren-sei opening. As a side note, the O's form the ni-ren-sei.
The name comes from the fact that the 4 4-4 points and the 4 10-4 points on the board are called hoshi points. San-ren-sei literally means 'three stars in a row'.
This kind of opening was unheard of in classical go (which stressed territory), but came into use during the Shin Fuseki era ushered in by Go Seigen and Kitani Minoru. The traditional opposition to the 4-4 move in the corner is that it DOES NOT secure corner territory. The modern acceptance of the move stems from the consensus that the exchange of secure territory for 'influence' or 'thickness' is sufficient. Another benefit of the 4-4 play is speed, in that the 4-4 point plays aim to settle the corner situation with one play. The 10-4 stone attempts to make the two 4-4 points work together. This opening is somewhat influence oriented.
This opening is not very popular at higher levels of play, as secure territory is an important factor. However, no one would claim that the san-ren-sei is a bad opening strategy.