There are two main types of ANOVA (Analysis of Variance) - One-Way and Two-Way. One-way or two-way refers to the number of independent variables in the test.

One-Way ANOVA

A one-way ANOVA assesses the effect of a single factor on a single response variable. It is used to determine whether there are any statistically significant differences between the means of three or more unrelated groups. For example, one-way ANOVA can be used to study the effects of tea (black tea, green tea, no tea) on weight loss by splitting a group of individuals into three groups. 

Two-Way ANOVA

A two-way ANOVA is used to determine the effect of two independent variables on a single dependent variable. It is used to study the interaction between the two independent factors and tests the effect of two factors at the same time. Two-way ANOVA is an extension of the one-way ANOVA. Whereas there is one independent variable affecting one dependent variable in one-way ANOVA, in a two-way ANOVA there are two independents. For example, a two-way ANOVA can be used to compare employee productivity based on two independent variables such as skill set and salary.