Long woven wraps, also called "baby wraps," are long woven pieces of fabric. Strong enough to support a child for years, these wraps can have varying qualities based on their weight/thickness (gsm), their weave (broken twill, herringbone, jacquard, etc.), and the fiber content (cotton, linen, Tencel(R), etc.). Long woven wraps are strong, soft, supportive, and extremely versatile, making this an excellent carrier from newborn through toddler and beyond, for any caregiver/child pairing.
Most start with base size, and the most popular base size is a 6. Here are more details on sizing to help you choose: https://mama-roo.com/blogs/gentle-pregnancy-and-parenting/what-size-wrap-do-i-need-long-woven-wrap-sizing
Low number gsms (less than 200) are very thin and light
Mid-range gsms: 200-300
High gsms: These are heavier wraps that are often well suited to older children
Gsms under 240 may not be "cushy" enough to be comfortable for the wearer in supporting a toddler, though they are still safe.
Happy wrapping! Feel free to reach out with any questions. Many find trying a variety of styles works well for them.