Complex sentence: In the English language, catenative verbs are verbs which can be followed within the same clause by another verb, in either the "infinitive" (both full and bare) or "present participle/gerund" forms.
Split into simpler sentences: In the English language, catenative verbs are verbs which can be followed within the same clause by another verb. This second subordinated verb can be in either the "infinitive" (both full and bare) or "present participle/gerund" forms.