What is a False Teacher?

What is false teaching and what is a false teacher?Are there theological errors that do not rise to the level of false teaching?Is it possible to be too quick to label someone a false teacher? Also, how do we balance charity and firmness in this process?False teaching was a serious issue in the church in the early church. Is it really still an issue in the church in America? What is the risk connected to false teaching?How do we spot false teaching in the church, and what do we do about it?Are there ways a church can safeguard against false teaching?Listener questions:What does it mean to take the Lord’s Supper in an “unworthy manner?”