An anchor chart is a tool used to support instruction. They are a way to help students be more successful in your classroom. They may have classroom expectations on them. They may have friendly reminders of daily procedures. An anchor chart could be as simple as a formula which students regularly need. An anchor chart could be up all year, be used for one unit, or could evolve throughout the course of the year. Many times they are just "friendly reminders" or "things to think about" for students to look at if they "forget" the next step or process.
Anchor charts are often created collaboratively with the students but do not need to be. They can be hand-written or typed. They can be purchased from a store and tweaked or "stolen" from a fellow teacher.
How can you use anchor charts effectively? Point them out when students should be referencing them during a lesson. If you don't, then they are just decorations on the wall. Have students create or add to the anchor charts, throughout the unit or year.
If you want ideas of what you could use in your classroom, check out the awesome anchor charts already in our building. (There are many more but I couldn't include them all.) Or Google it! There are so many great resources out there, so use them!