How The Software Performs Multiple Tasks At Same Time
Sometimes you need to perform simultaneously multiple sets of operations at the same time. For example instead of searching one keyword at a time you may want to perform keyword research for 3 keywords at the same time. So this concept is called as multi-threading. In cases like this you can choose the setting called "speed" and the higher the number the software will do more tasks simultaneously, and try to give faster results.
Example
In the above example instead of choosing one keyword, we have chosen 2 keywords at the same time. The software will harvest the data for both keywords simultaneously and not one after another. In many other cases software will not allow multi-threading but allow to add only one keyword because sometimes trying to get data too fast will result in the banning of the IP. So, the cases where multi-threading can be used, we have used in the software's and where it can be a risk we are not using.
In such cases the data harvested will take place linearly one after another and not at the same time (multi-threading)