Difference between Sort and SortByColumns in PowerApps

Description:

Table Name "ACCOUNT"

Field Name "AccountName"

Sort: 

Consider i have a COMBOBOX Available i need to show the AccountName in the ComboBox.

So i Set ITEMS of ComboBox = "Account"

Now i want to Sort the Table Account in the Combobox using Account Name, What i can do. I can user SORT query there 

Sort(Account,"AccountName",Ascending)

Account - DataSource (table)

AccountName - Column (Column in Table)

Ascending - Sorting Type (Ascending/Descending)

SortByColumns: 

Now i want to Sort the Table Account in the Combobox using ONLY Account Name, What i can do. I can user SORT query there 

SortByColumns(Account,"AccountName",Ascending)

Account - DataSource (table)

AccountName - Column (Column in Table)

Ascending - Sorting Type (Ascending/Descending)