Learn Hardcore Korean: setakgie ppallaereul neohgo sejereul neoheuseyo. - Put the laundry in the washing machine and add detergent.

The particle -에 marks a location or goal (“into/at”), so 세탁기에 means “into the washing machine.” If you said 세탁기를 넣다, it would mean “put the washing machine (somewhere),” which isn’t what we want.

What role does -를 play in 빨래를 넣고?

-를 is the object marker. It tells you the direct object of the verb 넣다 (“to put in”). So 빨래를 넣다 means “put the laundry in.”

What does the connective -고 do in 넣고 세제를 넣으세요?

The ending -고 links two actions in sequence: “put the laundry in and then put the detergent in.” It’s like using “and” between two verbs in English.

What level of politeness is the verb ending -세요?

-세요 is the polite (also called “standard” or “informal polite”) imperative ending. It’s used when giving instructions or commands to someone you’re not extremely close to, like customers or classmates—polite but not overly formal.

Why is there no subject in this sentence?

In Korean, if the subject is obvious or has been mentioned, you often omit it. Here, it’s clear you (the listener) are the one doing the washing, so you drop 당신은 or 너는.

What’s 세제 exactly?

세제 means “laundry detergent” or “soap.” It’s the cleaning agent you add to the washing machine.

How would you say this instruction in casual (반말) form?

You can drop -세요 and use -어/아 endings:
세탁기에 빨래 넣고 세제 넣어.