That language is an explicit part of Israel - the Declaration of Independence enshrines the idea that Israel is, first and foremost, a Jewish state. In more recent times, the nature of the state is often referred to as "Jewish and democratic". It is also enshrined in the basic laws of Israel (Israel doesn't have a constitution).

This entire concept has a dedicated article on Wikipedia [0]. It's a pretty fun read for those that believe Arab(or those of other non-Jewish ehtnicities, though they are far fewer) citizens of Israel are fundamentally equal to Jewish citizens of Israel.

Basically, Israel is all for equality, but with some limits - essentially, it would not be acceptable for people who are not Jewish to have an outsize power in Israel, though they are free to participate as minority parties. This is, in my opinion, the main reason why Israel has never attempted to annex the Palestinian territories. The Arab majority (or near majority today) that would form in the population would seriously challenge the idea of a Jewish and democratic state - they would be forced to stop recognizing Arabs' right to vote and/or hold office.

[0] https://en.wikipedia.org/wiki/Jewish_and_democratic_state