There are three command block types in both Bedrock Edition (previously known as Pocket Edition) and Java Edition (on PC):
Impulse, the default when you place down a command block, where the command block is orange.
Chain, where the command block is a cyan/green color.
Repeat, where the command block is purple.
You can change the type of command block by tapping on it and then select the drop down menu, or by specifying the type of command block in the
/give @s chain_command_block
/give @s repeat_command_block
These other command block types are a bit more complicated than the default type, but basically, a repeat command block repeats the command entered for as long as it is powered, and the chain command is used in sequences of command blocks, and fires after the command block behind it has run. They have to placed so that all the arrows are facing in the same direction to make sure that they actually run.
I highly recommend checking out the official Bedrock Creator Documentation for more in depth information, and info that is specific to this version of Minecraft. These articles should be helpful:
Additionally, you can check out this article if you want to learn more about the history and differences between Minecraft versions. If you're still a little confused about using the different command block types and want a more visual explanation, try a YouTube tutorial like this one.
Feel free to ask any more questions you have either in the comments here or in a separate question, just make sure to include enough detail that we can understand your problem and how we can help. Good luck on your command journey!