Inserted Table ?

Trying to get my head around this table:

I thought it contained all data used in an insert; meaning if i enter a row in a table the inserted table should then contain all data entered?

Ive created multiple tables linked via primary key Learner_ID this key is unique to any/all students and can never be duplicated hence i thought i would use it to link the tables.

I have tables Fab / Main / Elec / Learner_info / WS_WR.

For Fab / Main / Elec the only data i need form Learner_info is the Learner_ID field, i simply used:

INSERT INTO FAB(Leaner_ID)
SELECT Learner_ID
FROM Inserted

as a trigger to insert the ID into these tables. Everything works perfectly fine. So i assumed that i would be able to use something very similar to insert say:

Learner_ID, FNAME, LNAME, ONAME and C_NUM from the learner_info table into the WR_WS table. Apparently i was wrong I can insert the learner_ID perfectly but if i then try to add another insert trigger eg: insert fname i get an sql error:

Cannot insert the value NULL into the column 'LEARNER_ID', table 'swdt_im.WS_WR'; column does not allow nulls. INSERT fails.

Now from reading the error it suggests to me that because the second trigger is running my learner_id value has become a NULL. Obviously a primary key wont accept this value so the statement fails.

What im struggling to understand, im sure i will solve the problem eventually but i would apreciate help, and this is most important to me rather than a solution is this:

If i enter data into a row on a table does that data go into the inserted table in the same row? or does the data go into inserted as a single entry row, meaning when i tab along from learner_ID into FNAME does Learner_ID become row 1 (in inserted) and FNAME the current row? or do they go into the appropriate columns?

I was under the assumption that i could enter:

LEARNER_ID / FNAME / LNAME / ONAME / C_NUM

into one table and have a trigger insert those values into multiple other tables. Dont suppose someone can help me out im alright querying a SQL db but ive never had to develop anything other than a single table one myself before

Thanks in advance