A curriculum is a course of study. For example, the Saxon publishers, produce a series of math books which provide students a course of study in basic through advanced levels of math. One of the main tasks of the homeschool parent is to find curricula that meets their children's needs, suits the parents style of teaching and fits the family's schedule. There are many things to consider when choosing it and this is an area that can be overwhelming for new homeschoolers.
I have listed a few publishers below, but there are many, many others. The best thing to do is to attend a homeschool convention where there are numerous vendors available to answer your questions and you can look at the curricula first hand. Curricula is a tool. You do not have to do everything it tells you to in the teacher's manual. Use what you want and how you want to use it.
There are too many to list all of them. These are just a few of my favorites. Christianbook carries nearly everything. Every time I try to search for a particular publisher, Christianbook comes up, so visit there first.
www.christianbook.com www.rainbowresource.com www.sonlight.com https://www.bjupress.com/page/Home https://www.jeanniefulbright.com/ https://www.masterbooks.com/homeschool-curriculum/subject. https://answersingenesis.org/store/curriculum www.abeka.com Foundation for Christian Education (www.face.net? Rod & Staff (https://www.milestonebooks.com/list/Rod_and_Staff_Curriculum/