They are called the tram lines
If you are playing tennis and there is one person on both sides of the court it is called singles. If there are two people on both sides of the court it is called doubles.
Two players on each side compete in a tennis doubles match.
In tennis there is singles, and doubles. In both there is playing baseline/server, alley/net/volley.
On a tennis court, there will be four rectangles along the side edges. The inside line of those boxes are called the singles sideline. When playing doubles, you use the full court, including those boxes. When playing singles, you exclude those boxes as part of the playing field.
The two longest outside lines on a tennis court are called the doubles lines or doubles sidelines.
The inside line is the boundary for tennis when playing singles. The outside line is the boundary in Doubles.
Try Miniclip.com for games called Tennis Ace, doubles and so on
Tennis played with two players on each side is called doubles tennis.
the area that you serve into is the same as in singles. The server may stand anywhere in between the center mark and the doubles sideline