I think he's asking "what are mods" as in when someone says "you need speed mods."
The answer is both. Attributes like "speed" can be a primary stat, a secondary stat, and a set.
For sets, that's the large icon on the mod. You need to place either 2 or 4 together to get a set bonus for a particular set (speed sets increase speed, health sets increase health, etc.)
Next, you can also have speed primary stats. This is the big text directly under the icon on the mod. For example, you can get an arrow mod that gives you +30 speed. This speed primary arrow mod can be of any set (speed, health, defense, etc.).
Lastly, you can have speed secondary stats. These are the 4 different stat under the primary stat. For example, you can have an health arrow with +25% protection and a speed secondary of +13 speed. Every mod has 4 speed secondaries. For gray mods, you get 1 boost of each of the 4 secondaries. For green mods, you get 5 boosts, which mean one of the 4 secondaries will get boosted twice. For blue mods, you get 6 boosts, which means you get 2 additional boosts which can land on the same or different secondaries (25% chance to land on any of the 4). As the colors go up, you get an extra boost to a secondary.
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Not sure what your question is asking.
I think he's asking "what are mods" as in when someone says "you need speed mods."
The answer is both. Attributes like "speed" can be a primary stat, a secondary stat, and a set.
For sets, that's the large icon on the mod. You need to place either 2 or 4 together to get a set bonus for a particular set (speed sets increase speed, health sets increase health, etc.)
Next, you can also have speed primary stats. This is the big text directly under the icon on the mod. For example, you can get an arrow mod that gives you +30 speed. This speed primary arrow mod can be of any set (speed, health, defense, etc.).
Lastly, you can have speed secondary stats. These are the 4 different stat under the primary stat. For example, you can have an health arrow with +25% protection and a speed secondary of +13 speed. Every mod has 4 speed secondaries. For gray mods, you get 1 boost of each of the 4 secondaries. For green mods, you get 5 boosts, which mean one of the 4 secondaries will get boosted twice. For blue mods, you get 6 boosts, which means you get 2 additional boosts which can land on the same or different secondaries (25% chance to land on any of the 4). As the colors go up, you get an extra boost to a secondary.
If that's too confusing, read this page:
https://gaming-fans.com/swgoh-101/swgoh-101-comprehensive-mod-guide/#ModBasics