Buổi đổi đồ bắt đầu cuối tuần này.

Here, buổi means session, occasion, or event.

It does not mean only morning. In Vietnamese, buổi can be used for parts of the day, as in buổi sáng or buổi tối, but it can also mean a particular event or session.

So buổi đổi đồ means something like the swap event or the item-swapping session.

It depends on context.

• đổi = to change, exchange, swap
• đồ = things, stuff, items, clothes

So đổi đồ can sometimes mean change clothes, but in the context of an event, it often means swap items or exchange things.

That is why context matters a lot with đồ.

Because Vietnamese often puts the main noun first and the describing part after it.

So in buổi đổi đồ:

• buổi = the main noun, meaning event/session
• đổi đồ = describes what kind of event it is

Literally, it is structured more like event of swapping items than like English swap event.

The sentence breaks down like this:

• Buổi đổi đồ = the swap event
• bắt đầu = begins / starts
• cuối tuần này = this weekend

So the structure is:

[subject] + [verb] + [time expression]

Vietnamese often follows this straightforward order.

Vietnamese usually does not use articles the way English does.

So a noun phrase like buổi đổi đồ can mean:

• a swap event
• the swap event

The exact meaning depends on context.

English requires an article, but Vietnamese often leaves that information unstated unless it needs to be made clearer in some other way.

Because the time expression cuối tuần này already shows that the event is in the future.

Vietnamese often does this:

• If the time is clear, no future marker is needed.
• sẽ can be added, but it is optional here.

So both are possible:

• Buổi đổi đồ bắt đầu cuối tuần này.
• Buổi đổi đồ sẽ bắt đầu cuối tuần này.

The version without sẽ sounds very natural.

Literally, cuối tuần này is the end of this week.

In natural usage, though, it is very often understood as this weekend.

So in many everyday contexts, those two ideas overlap. If the sentence is about an event, this weekend is usually the most natural English interpretation.

In Vietnamese, words like này and đó usually come after the noun or noun phrase they modify.

So:

• tuần này = this week
• cuối tuần này = this weekend / the end of this week
• ngày này = this day

This is different from English, where this comes before the noun.

No, you do not need it.

Vietnamese often allows time expressions without a preposition. So:

• Buổi đổi đồ bắt đầu cuối tuần này.
• Buổi đổi đồ bắt đầu vào cuối tuần này.

Both are natural.

Adding vào makes the time relationship a little more explicit, similar to saying starts at/on this weekend, but it is often omitted in normal speech and writing.

Mostly yes.

bắt đầu means to begin or to start. In this sentence, it works as the main verb:

• Buổi đổi đồ = subject
• bắt đầu = starts
• cuối tuần này = this weekend

So bắt đầu functions very much like English start in The event starts this weekend.