StackAndTile considers tables to be one of four types:
1. New Tables
2. Stacked Tables
3. Tiled Tables (Grid Tables)
4. Old Tables
Any table that StackAndTile has not yet encountered will be deemed as a 'New Table'. The simplest example is when you initially press Start, every poker table (of your included sites) will be seen in SaT as a 'New Table'. Another time a table will be seen as 'New' is when you open a new table mid-session. So if you have 4 tables open and playing with SaT, and you were on a waitlist and that 5th table pops up, this table will be marked as 'New'.
The 'New Tables' are only relevant because you might want these to be handled specially. Lets say your 4 table grid layout consumes your entire screen. Your 5th table that was waitlisted opens up, blocking your vision of other tables that require attention. The tables that require action are more important, because you are in the middle of hands; the 'New' table is merely waiting for you to take a seat and buy in. So, SaT can move these New Tables for you so that they don't interfere, depending on where you want your New Tables to be placed.
Stacked Tables are those that are all in the same location on the screen, piled on top of each other. By putting tables on top of each other, you can save screen space and play more tables simultaneously. The problem is, since you can't see every table, how do you know when its your turn to act? SaT takes care of all that. All tables that are 'Stacked' will be scanned to determine whether it is your turn to act requiring your action. Then, depending on your 'Tile Setting', the table will be handled accordingly.
SaT does not consider a table to be 'Stacked' until you specifically stack it with a stacking hotkey (such as 'Stack table' or 'Fold+Stack table'), or if you click the Fold button with your mouse (while Left Click Detection is on). The one exception to this is if choose your New Tables slot setting to be the same as your Stack slot setting. Then all New Tables will be automatically stacked and considered as a Stacked Table.
Tiled Tables (Grid Tables)
If you press the Visualize Grid button, you will see your grid layout. Any table that is in a slot other than your stack slot is considered to be a 'Tiled Table' (or a 'grid table'). So for example, if you have a grid layout for 4 slots, and you use slot 1 for your stack, then slots 2,3,4 are for grid tables. Once tables are moved out of the stack and into the grid, they will remain there until you click the Fold button during the hand, or until you send a stacking hotkey to the table, at which point the table will return to the Stack.
Tables leave the stack and become Tiled in a few different ways. First, any table can be manually chosen by the user to be tiled and moved into the next free grid slot, by way of using the 'Move table to next slot' hotkey. The other ways that a table will get Tiled and moved into the grid depends on the 'Tile Setting'. If your Tile Setting is on "Action required", then the table will be moved and tiled into the grid as soon as it is your turn to act, putting it in the grid where you can focus on it. If your Tile Setting is on "After entering pot", then the table will not be moved when it is your turn to act, but only after you've taken a call or bet action to enter the hand.
These refer to tables that have not required action for a certain period of time. SaT will keep track of how long its been since a table has last required your action. If that time has elapsed, the table will be marked as 'Old' and handled accordingly to the option chosen. This affects tables that you might have timed out on (and are now sitting out), or cash tables where everyone leaves, etc.
By default, any table that hasn't required action in the last 5 minutes will be considered 'Old', and will move in to the grid where you can see it, and then determine what to do with it. That way, instead of the table being lost in the bottom of the stack somewhere where you cannot see it, after 5 minutes of no decisions on the table, it will be moved into the grid (or closed completely if you choose). You can also choose how long to wait if you think 5 minutes is too long/short. The 'Old Tables Duration' setting can be found in Advanced Options.
One thing to note about Old Tables, they will only start being detected AFTER the first action is required. For example, if you open up an empty cashgame table and take a seat and wait for an opponent, you could be waiting hours. However, since no action was ever yet required on the table (the fold button hasn't yet been visible), then this table will NOT be treated as Old. Only after the first action is required, then will SaT start checking the minutes since the last action.