Number/Demonstrative + 个 + Noun
个 (gè) is the most common and versatile classifier in Chinese, used when no specific classifier is designated for a noun. It appears between a numeral or demonstrative and the noun it quantifies. While many nouns have dedicated classifiers, 个 can serve as a default in everyday speech.
他是一个很有意思的人。
tā shì yí gè hěn yǒu yìsi de rén.
He is a very interesting person.
我想吃一个苹果。
wǒ xiǎng chī yí gè píngguǒ.
I want to eat an apple.
那个地方我去过好几个了。
nàge dìfang wǒ qù guo hǎo jǐ gè le.
I've been to quite a few of those places.