The game mechanic Worker Placement or more precisely Action Drafting requires you select an action that is available to all players in a game. It is the most popular of the Euro-style games.
In many games you have a token or meeple that represents a worker to be placed on a certain area on the board to perform a task. It is usually a turn based game and when an action is used, no other player can play that action in the round or in some cases, they have to pay to use special ability or card to perform that same action.
For instance, in the game Lords of Waterdeep, there are squares where you put your meeple on to get resources, get a quest, or use special cards. Here a green meeple is placed on a square to receive 2 orange cubes (or warriors). No one else can use that resource during the round unless they have a special card or ability that lets them which usually requires a cost. There are many more of these spaces on the board that gives out resources or special cards or use a special card.
The example above is from the game Agricola. The red and blue circles are farmers. You get two farmers at the beginning of the game to do tasks. One red farmer is getting 1 clay which is a resource. No one else can use that action of getting 1 clay during the round.
The first player is not always the same person during the game. This is important as the first player of the round will get first choice on available actions. Some games lets you choose to be the first player the next round but it requires you use your worker token to get that.
Also many games introduces more actions as the games progresses whether by buying a card that offers a new action or a round reveals a new action as in Agricola.
This is requires a lot of strategy as you can be denied important resources or actions during an entire round, so you want to try to be the first player. Or you use a different strategy as the first player so you can choose a resource you know the first or preceding players will not likely to use.
I only played Lots of Waterdeep and Agricola, but there are other worker placement games to look into like Stone Age, Kingsburg, Alien Frontiers, Caylus, anymore.