What does 即 mean in ...Google在ICML文中描述的非常清晰，即在每次SGD时...?
即 itself can mean "equal".  For example: '五人即一伍' (Five men equal one unit)

~ you can replace 即 (equal) with 為(be), For example:  '五人為一伍' (Five men is one unit)

But 即 can be short for 即是 (namely; that is to say; to be specific)

Example:

[1. 軍隊將士兵分伍] [2. 即] [3.每五人組成一個單位]

[1. Amy divides soldiers into 伍] [2. to be specific ] [3. Every five people become one unit]

[1. general statement] [2. to be specific] [3. detail description]