toのつかない不定詞を原形不定詞と言う。

tbd

An infinitive without a 'to' attached is called a bare infinitive.

動詞helpはto不定詞・原形不定詞の両方をとりますが、くだけた文体では原形不定詞が多いとされており、この例文でもそれが使われています。

tbd

The verb 'help' takes to-infinitives and bare infinitives but bare infinitives are said to be the most common in casual text; as also used in this example sentence.