When Tokyo Ghoul Season 3 (or the first season of the Tokyo Ghoul:re anime) was announced the number of episodes was listed as ending at Episode 12. Considering how long the Tokyo Ghoul:re manga series has become in 2018, that number seemed kind of paltry to fans. Now, Yonkou Productions has confirmed that a second cour of 12 episodes is scheduled by Studio Pierrot, but the release date will be in October of 2018. That means the Tokyo Ghoul:re anime series is taking a break for the 2018 summer anime season.
Considering that there is a seasonal gap between the episodes, some anime fans may prefer to label the next set of 12 episodes as either Tokyo Ghoul Season 4 or Tokyo Ghoul:re Season 2. However, this scheduled release is technically known as a split-cour anime, which means that it's the second part of Tokyo Ghoul Season 3.
This confusion is largely caused by the differences in how Japanese TV labels seasons. Anime series are divided up into winter anime (January to March), spring anime (April to June), summer anime (July to September), and fall anime (October to December). Each three-month unit of broadcasting is called a "cour." Any Japanese anime season that runs continuously for more than these 10 to 13 episode units is referred to as having multiple cours for a single season.
In the case of Tokyo Ghoul Season 3, it's a rare example of a split-cour anime. By Western standards, the new episodes should be called Tokyo Ghoul Season 4 since there is going to be a large break in the broadcast, but a split-cour anime is when a single season takes a break for a single three-month unit of time. As another example, the current fourth season of the Food Wars! anime is labeled by the studio as being the second cour of Shokugeki no Souma: San no Sara.
It's currently unknown how Studio Pierrot will label the upcoming fourth season or whether the title will reflect being a split-cour at all. From the average anime viewers' perspective, all these technicalities involved in labeling the seasons do not matter much. What does matter is that anime fans will be able to watch more Tokyo Ghoul:re episodes sooner than expected.
For those wanting more information or spoilers, please see the Inquisitr's main article about Tokyo Ghoul Season 4, which is updated as news comes out.