Sub UpDateSheet ()...............[I can use this as is because it is global - correct?]
Yes it will update all cells from all textboxes

for x = 1 to 190.............[What does "x" signify?
X will count from 1 to 190

Do I need to change it to mean something specific to my userform and/or worksheet?]
Worksheet yes ... Userform - Not if your textboxes have their default names - Textbox1 etc


Sheet1.cells (X,1) .value = Me ("Textbox" & X) .Text..............[Should I change Sheet1.cells to my specific worksheet name?......
Yes.. You will see the name in the VBE project explorer.. The given name is in brackets

What does the "(X,1) signify?......Do I need to change ("Textbox"...to a specific textbox?]
Cells(X,1) specifies row X, column 1........ In this case it writes the value of the textboxes sequentially into column A.. This is just notional for demo and will need to be amended to suit your spreadsheet.

next x................[enter as is or does the "x" need to be something more specific to my userform and/or worksheet?]
As is... It's a composite part of the For X loop and sends the computer back to the "For" line if X is less than the max value (192)

You're more than welcome