yeongsujeungeun beoriji malgo jeobeoseo jigabe neoheo dwo.

Here, -은 is the topic marker. It highlights the receipt as the thing being talked about.

So 영수증은 버리지 말고... feels like:

• As for the receipt, don’t throw it away...
• or more naturally, Don’t throw away the receipt...

Using -을/를 instead would focus more directly on the object of 버리다 (to throw away), but -은 gives a contrastive or topical feeling, like the speaker is singling out the receipt in particular.

For example, it can imply something like:

• The receipt, at least, don’t throw away.

This kind of topic marking is very common in Korean and often sounds natural even where English would not explicitly mark a topic.

버리지 말고 comes from:

• 버리다 = to throw away / discard
• -지 말다 = to not do something
• -고 = and, and then, instead of

So:

• 버리지 말고 = don’t throw it away, and...
• more naturally: instead of throwing it away, ...

This pattern is very common:

• 가지 말고 여기 있어.
  Don’t go; stay here.
• 혼자 하지 말고 같이 해.
  Don’t do it alone; do it together.

So in your sentence, 버리지 말고 connects to the next action:
Don’t throw away the receipt—fold it and put it in your wallet.

Good question. Both relate to negative commands, but they work differently.

• 마 / 말아 / 마세요 = a direct negative command by itself
• 말고 = don’t do X, and instead do Y

Compare:

• 버리지 마.
  Don’t throw it away.
• 버리지 말고 접어.
  Don’t throw it away; fold it instead.

So 말고 is used because the sentence continues into another action.

접어서 comes from:

• 접다 = to fold
• -어서 / -아서 = and, then, after doing

So 접어서 means:

• fold it and...
• after folding it...

In this sentence, it links the action of folding to the next action:

• 접어서 지갑에 넣어 둬
• fold it and put it in your wallet

This -아서/-어서 form often shows that one action leads naturally into the next.

Examples:

• 문을 열어서 들어가.
  Open the door and go in.
• 종이를 접어서 넣어.
  Fold the paper and put it in.

Because Korean often omits objects and subjects when they are obvious from context.

Here, 영수증은 is introduced at the beginning, so after that, Korean does not need to keep repeating the receipt / it.

English would usually say:

• Don’t throw the receipt away; fold it and put it in your wallet.

Korean naturally says:

• 영수증은 버리지 말고 접어서 지갑에 넣어 둬.

The omitted object is understood throughout as the receipt.

지갑 means wallet, and -에 marks the location or destination.

So:

• 지갑에 넣다 = put [something] into/in the wallet

With verbs like 넣다 (to put in), -에 marks the place something goes.

Examples:

• 가방에 넣다 = put into a bag
• 서랍에 넣다 = put into a drawer
• 주머니에 넣다 = put into a pocket

So 지갑에 넣어 둬 means put it in your wallet.

넣어 둬 is from:

• 넣다 = to put in
• 두다 = to leave, keep, set aside
• 넣어 두다 = to put something somewhere and leave it there / keep it there for later

So this adds an important nuance.

• 넣어 = put it in
• 넣어 둬 = put it in and keep it there / put it in for future convenience

In this sentence, 넣어 둬 suggests:

• Put it in your wallet and keep it there
• Store it in your wallet so you have it later

This is a very common Korean construction:

• 써 둬. = write it down and leave it written
• 문 열어 둬. = open the door and leave it open
• 냉장고에 넣어 둬. = put it in the fridge and keep it there

They are very close.

• 넣어 둬 is the basic form of 넣어 두다
• 넣어놔 is a contracted spoken form of 넣어 놓다

In modern Korean, -아/어 두다 and -아/어 놓다 often overlap a lot in meaning, especially in everyday speech. Both can mean doing something in advance and leaving it that way.

So these are similar:

• 지갑에 넣어 둬
• 지갑에 넣어놔

Both mean something like put it in your wallet and keep it there.

That said, learners are often first taught -아/어 두다 as do and keep it that way / do it in preparation, and -아/어 놓다 can also carry that idea. In casual spoken Korean, the difference is often not very important.

둬 is a casual intimate form, used with:

• close friends
• younger people
• children
• family members, depending on the relationship

So this sentence is not polite.

The polite version would be:

• 영수증은 버리지 말고 접어서 지갑에 넣어 두세요.

Or a slightly softer conversational polite form:

• 영수증은 버리지 말고 접어서 지갑에 넣어 둬요.

So:

• 넣어 둬 = casual
• 넣어 두세요 = polite

It can feel like any of those depending on context, but grammatically it is basically a casual command/request.

Because of -지 말고 and -어 둬, the speaker is telling someone what to do:

• Don’t throw away the receipt; fold it and put it in your wallet.

In real life, the tone could range from:

• firm instruction
• practical advice
• a casual reminder

Korean often leaves that distinction to context and tone of voice.

Korean usually presents actions in the order they happen.

So this sentence goes step by step:

1. Don’t throw it away
2. Fold it
3. Put it in your wallet
4. Leave it there / keep it there

That makes the sentence feel very natural and procedural.

English often works the same way, but Korean especially likes linking actions in sequence with forms like:

• -고
• -아서 / -어서
• -아/어 두다

So the structure is very typical Korean action chaining.

Yes. Even though the reason is not stated, 넣어 둬 often implies keeping it for later use.

For example, maybe:

• you might need it for a return
• you need it for reimbursement
• you want to keep proof of purchase
• you may need it for records

Korean does not need to say that explicitly. The nuance of put it there and keep it there is already built into 넣어 둬.

So the full feeling is something like:

• Don’t toss the receipt—fold it and keep it in your wallet for later.