Overview of SAP Tree Model Classes 
The class CL_SIMPLE_TREE_MODEL is the ABAP Objects wrapper for the simple tree.
Example program: SAPSIMPLE_TREE_MODEL_DEMO:

A node consists of a folder or leaf symbol and a text.
You cannot use checkboxes or additional icons.
You can only have one text for each node.
There is no heading.
The class CL_COLUMN_TREE_MODEL is the ABAP Objects wrapper for the column tree model.
Example program: SAPCOLUMN_TREE_MODEL_DEMO:

A node consists of a folder or leaf symbol and a range of items.
The entries of a node are arranged in columns.
Example
In the example, the tree has three columns with the logical names 'Column1', 'Column2', and 'Column3'. The topmost node has an entry in each of these columns:
'Root Col. 1' in column 'Column1'
'Root Col. 2' in column 'Column2'
'Root Col. 3' in column 'Column3'
A column tree can contain two kinds of columns:
Columns in the hierarchy area: These columns are below the hierarchy heading. The hierarchy heading is the first heading from the left in the tree (in the example, 'Hierarchy Header'). There is normally only one column in the hierarchy area. In the example, it is the column with the name 'Column1', containing the entries 'Root Col.1', 'Child1 Col. 1' and so on.
Columns outside the hierarchy area: These columns have their own heading. The example contains two columns outside the hierarchy area, with the headings 'Column2' and 'Column3'.
Columns can have the following kinds of entries:
Text: Text, with optional icon
Checkbox: Checkbox with optional icon and text.
Pushbutton: Pushbutton with text and icon.
Link: Like text, but additionally, an event is triggered when the user clicks the link.
The class CL_LIST_TREE_MODEL is the ABAP Objects wrapper for the column tree.
Example program: SAPLIST_TREE_MODEL_DEMO:

A node consists of a folder or leaf symbol and entries.
The entries are displayed from left to right.
Example
Structure of the first three nodes in the example:
The topmost node has a single entry ("objects"). Proportional font is set for this entry. Additionally, the "automatic width" is set. This means that the width of the entry is adjusted to fit the contents (in this case, the string "objects").
The second node from the top has the same construction as the first: An entry with the text "Screens".
The third node from the top has four entries:
A tick icon, four characters wide.
0100, not in proportional font, four characters wide.
MUELLER, not in proportional font, 11 characters wide.
Comment for screen 100, proportional font, automatic width.
Using non-proportional fonts and a fixed display width allows you to display data in tabular format, as in the example.
Columns can have the following kinds of entries:
Text: Text, with optional icon
Checkbox: Checkbox with optional icon and text.
Pushbutton: Pushbutton with text and icon.
Link: Like text, but additionally, an event is triggered when the user clicks the link.
There is a hierarchy heading and a list heading, under which all entries can be grouped.