Defensive Lineman - A player on the defense who plays on the line of scrimmage. This includes defensive tackles and defensive ends.There are two defensive ends and either one or two defensive tackles on the field during each defensive snap.
The defensive tackle is positioned on the inside of the defensive line, they stop the running back. There can be a nose guard which is when there is only one tackle on the line of scrimmage (3-4 scheme). When there are two tackles it is a 4-3 scheme.
Neither the end nor the tackle have a particularly high fantasy value when compared to other defensive positions. They do not get a lot of tackles and the majority of their points come from sacks and tackles for a loss, which are few and far in between. Tackles are the most valuable form of scoring in defensive player fantasy leagues.
Drafting a defensive linemen in the early rounds of a draft is a risky play. Those rounds are usually better to take stud linebackers, however if you can get one of the few elite talents you shouldn't pass on that. Guys like Aaron Donald and JJ Watt are superstars that definitely warrant a pick.
All defenders in IDP (individual defensive player) leagues receive the same amount of points for performing the same actions. However, defensive linemen due to them being on the line of scrimmage instead of the secondary do not usually perform all those actions. Below is a chart showing some common ways defensive linemen earn points as well as how many points each action is worth.
Noting that tackles are more common than sacks, they are much more effective in getting points. Defensive linemen that consistently get more tackles than their counterparts are highly valuable in IDP fantasy leagues.