Kansiosta löysimme kaiken, mitä jaoimme eilen.

Kansiosta is the elative form of kansio.

The ending -sta / -stä usually means out of / from inside something. So:

• kansio = folder
• kansiossa = in the folder
• kansiosta = from the folder
• kansioon = into the folder

So the sentence is talking about finding something from the folder or in the folder, depending on how natural the English translation is in context.

Also, kansio can refer to a physical folder/binder or a digital folder, depending on context.

Finnish word order is more flexible than English word order.

Starting with Kansiosta puts the folder first as the topic or point of focus. It is a bit like saying:

As for the folder, we found...

The sentence could also be said as:

Löysimme kansiosta kaiken, mitä jaoimme eilen.

That version is often more neutral. The original sentence gives a little more prominence to where the things were found.

Löysimme is the past tense of löytää, meaning to find.

It breaks down like this:

• löytää = to find
• löysimme = we found

It is:

• past tense
• 1st person plural
• so it means we found

In Finnish, the verb ending usually already tells you the person.

So löysimme already means we found, and jaoimme already means we shared / we distributed.

Because of that, Finnish often leaves out the pronoun me = we, unless it is needed for emphasis or contrast.

So:

• löysimme = we found
• me löysimme = we found, with extra emphasis on we

Kaikki is the basic dictionary form, meaning all / everything / everyone, depending on context.

In this sentence, the word is the object of löysimme. Because the action is seen as complete and the whole thing was found, Finnish uses the total object form here:

• kaikki = everything / all
• kaiken = all of it / everything, as a complete object

A very useful contrast is:

• löysimme kaiken = we found everything
• löysimme kaikkea = we found some things / all kinds of things / not necessarily the whole amount

So kaiken tells you the whole set was found.

Here mitä introduces a clause describing kaiken.

So:

• kaiken, mitä jaoimme eilen = everything that we shared yesterday

This is a very common Finnish pattern:

• kaikki, mitä...
• kaiken, mitä...
• se, mitä...

In this kind of structure, mitä often works like English what or that which. It is not a question word here, even though mitä? can also mean what?

So you can think of this whole part as:

everything that we shared yesterday

Jaoimme is the past tense, 1st person plural form of jakaa.

So it means:

• we shared
• we distributed
• we handed out
• we divided

The exact English choice depends on context.

Grammatically, it works just like löysimme:

• jakaa = to share / distribute
• jaoimme = we shared / distributed

Most naturally, eilen belongs to the clause mitä jaoimme eilen.

So the meaning is:

everything that we shared yesterday

not:

yesterday we found everything

If the speaker wanted to make yesterday refer clearly to finding, Finnish would usually place eilen differently, for example:

Eilen löysimme kansiosta kaiken, mitä jaoimme.

So in the original sentence, eilen most naturally modifies jaoimme.

Because mitä jaoimme eilen is a subordinate clause, more specifically a relative-type clause describing kaiken.

Finnish uses commas before this kind of clause more regularly than English does.

So the comma marks the beginning of:

mitä jaoimme eilen = that we shared yesterday

This is normal Finnish punctuation.

Yes. That is also a natural sentence.

The main difference is emphasis:

• Kansiosta löysimme kaiken, mitä jaoimme eilen.
  Emphasizes from the folder / in the folder
• Löysimme kansiosta kaiken, mitä jaoimme eilen.
  More straightforward, often more neutral

So the meaning stays basically the same, but the information is packaged a little differently.