space has both options of attachments and skinned clothing which you can use for uploading items and clothing to space.
There is a few differences between the two, and here are the details of the differences for you!
Attachments are just that- Attachments.
They attach to your avatar on a specific bone, for example, to the neck bone if you have created a necklace. You cannot attach the attachments to multiple bones.
Attachments also don't support deletion zones or advanced clothing features.
Attachments are much faster than skinned clothing performance wise, and they are much easier to upload and create as there are no rigging steps.
Skinned clothing are the normal full clothing items with rigging/weighting, and also with the addition of settings such as skin deletion and skin preservation.
Skin deletion is good to use if you have items of clothing which have areas cut out, such as trousers with lace up sides, or a dress with cut out side panels as you can select certain areas of the skin you want to delete.
Skin preservation works in a parallel way to the skin deletion - the areas of skin you select will be preserved.
This is good to use if you are also adding cloth physics to your clothing items as you can choose to preserve areas that might be shown when the cloth is moving around - e.g, you can choose to preserve the legs from the knee up if the cloth item is a skirt with physics, as you don't want the avatar's legs to disappear when the skirt is moving.