There is a well-known terminological ambiguity between econometrics and other statistics with regards to the "random effects" and "fixed effects". I feel that our tags add to this ambiguity, instead of clearing it up.
Mixed models are linear models that include random effects and fixed effects, i.e. random factors and fixed factors (or, rarely, only random factors).
The terms "random/fixed effects model" are never (?) used to refer to mixed models.Update: Mixed models are also sometimes called "random effects models".
In econometrics, a "fixed effects model" is a way to treat panel data which is equivalent to a standard linear model with only fixed effects. In contrast, a "random effects model" is a way to treat panel data which is formally equivalent to a mixed model with a random intercept but which is estimated via FGLS and not via MLE (as mixed models are). (Evidence: @StasK's 2012 Meta answer and my recent question on the main site.)
[fixed-effects-model] tag should only be applied to questions about econometrics; in practice people often use it on questions about mixed models to refer to fixed effects. This is confusing. And
[random-effects-model] tag can be, and is being used to refer to both, mixed models and random effects models in the econometrics sense. So the mixed models questions get split between these two tags, which is very unfortunate.
What could be the ideal arrangement?
I'd say: rename these two tags such that they unambiguously refer to econometrics. For example:
[panel-fixed-effects] (the word "econometrics" is too long to include in a tag name). And sort out the mixed models questions into