所 + Verb + 的 (that which is V-ed)

The (nominalizer)所suǒ structure

• (nominalizer)所suǒ + Verb + (of / 's)的de = "that which is (V-ed) / what (someone) V's".
• I / me我wǒ(nominalizer)所suǒto know知道zhī dào(of / 's)的de = "what I know"; everyone大家dà jiā(nominalizer)所suǒto be concerned about关心guān xīn(of / 's)的de = "what everyone cares about".
• (nominalizer)所suǒ…(of / 's)的de turns a verb into a noun-like "the thing V-ed".

(Subj) + (nominalizer)所suǒ + Verb + (of / 's)的de

• (nominalizer)所suǒ…(of / 's)的de packages an action into "the thing that is V-ed".

this这zhèis是shìI我wǒ(that which)所suǒknow知道zhī dào的deall一切yí qiè。

• I / me我wǒ(nominalizer)所suǒto know知道zhī dào(of / 's)的deeverything一切yī qiè = "everything (that) I know."

Recap

Read the full reference: HSK 6 grammar — Sentence patterns.