I assume you are referring to Obito's Kamui and Minato's Flying Thunder God.
The basics of both Jutsu's is kind of similar. In both the Jutsu, the user can transport himself from one place to another (normally known as teleportation).
Let's begin with Minato's Jutsu. According to Flying Thunder God Technique article on the wiki:
The Flying Thunder God Technique is a technique created by the Second
Hokage, Tobirama Senju, which allows the user to transport themselves
to a given marked location instantaneously. To activate this technique,
the user places a special seal or "technique formula" (術式,
jutsu-shiki) to mark an intended destination. After this is done, they
can enter a dimensional void at will that instantaneously transports
them to the location of the seal.
Now we come to Obito's Jutsu. According to Kamui article on the wiki:
Kamui allows the user to transfer anything to another dimension. Once
a target is sent to this dimension, it is unable to escape. This
technique, when used through Obito's right eye, is also able to make
the user "intangible" by transporting portions of their body to the
same pocket dimension.
- Kamui doesn't need any Mark or special seal for it to work.
- Kamui can only be performed if the user is using MangeKyou Sharingan,
whereas Flying Thunder God doesn't need Mangekyou Sharingan.
- Kamui creates space in different dimensions where the user can
transfer objects or himself and can stay in that dimension for
as much time as the user wants to, but in Minato's technique, the
user is immediately transported to a marked location.