[R] lm ANOVA vs. AOV

[Richard M. Heiberger]

The underlying least squares arithmetic of aov and lm is identical.
In R, the QR algorithm is used.  The difference between the two is
intent of the analysis and the default presentation of the results.

With lm [Linear Model], the focus is on the effect of the individual
columns of the predictor matrix.  The columns are usually interpreted
as values of real-valued observations.  The regression coefficients
are usually meaningful and interesting.

With aov [Analysis Of Variance], the focus is on the effects of
factors.  These are multi-degree of freedom effects associated with
categorical variables.  The arithmetic is based on a set of dummy
variables constructed from a contrast matrix.  The individual
regression coefficients themselves are not easily interpretable.

You can pursue the details of this summary in any good statistical
methods book.

Rich