We study compactoid and
compact filters which generalize the concepts of convergent filters and compact sets.
In particular, we investigate their properties in subregular and regular spaces, their
localizations, and their countable variants. Several classical results follow (e.g.,
theorems of Tychonoff, Kuratowski, Choquet). More recent results on preservation of
compactness (e.g., Smithson) and local compactness (e.g. Lambrinos) are extended
and refined.