A batsman in the sport of cricket is, depending on context:
The two batsmen have different roles:
While defending his wicket, the striker may also hit the ball into the field and attempt to run to the opposite wicket, exchanging places with the non-striker. This scores a run. The two batsmen may continue to exchange places, scoring additional runs, until members of the fielding team collect and return the ball to either wicket. See run (cricket) for further details.
While the striker's position is dictated by the necessity to defend the bowled ball from hitting his wicket, the non-striker typically takes a few steps away from his wicket as the bowler delivers the ball, in preparation to run.
Batsmen also have specialties within the skill. Some are opening batsmen (openers), meaning that they are the first players to bat in an innings. This specialty requires patience and fortitude to face the best opposition bowlers who are normally used first; typically these bowlers are fast bowlers, so an ability against fast pitched bowling is useful. In addition, a new cricket ball will keep its speed better when it bounces, which gives opening batsmen less time to play their shots. A new cricket ball will also have a tendency to move laterally when pitched as the seam is still prominent. However, an older ball may swing more or even reverse swing.
Following the opening batsmen are the middle-order batsmen (sometimes #3 is not considered middle-order). They are generally more free-scoring than the openers, partly because of their style and partly because the openers will have hopefully tired the bowlers and taken the shine and bounce from the new ball, so it should be easier to score runs.
After the recognised batsmen, the batting team's bowlers bat. Bowlers generally spend more time practising bowling, and so their batting is usually not as accomplished as the recognised batsmen. Particularly bad batsmen are known as rabbits. On occasion some truly woeful batsmen have been referred to as ferrets as 'they go in after the rabbits.'
Australian cricketer Sir Donald Bradman, "The Don", is universally accepted as the greatest exponent of the art of batting that the game has ever seen. His record is without peer.
Some players, known as all-rounders, are reasonably good at batting and bowling and may occupy any position in the batting lineup but few are opening batsmen and obviously none is a rabbit (or they wouldn't be all-rounders!).
The wicket-keeper also bats and is expected to be at least an adequate batsman: the choice of wicket-keepers for international teams is often influenced by their batting ability.
All of the above are generalisations and many exceptions can be found in the history of cricket.