Insourcing is a term which originally described creating a separate unit within a company or on-site to perform a task or tasks normally performed by other parts of the company. An example might be establishing a single unified call center to handle incoming calls for all departments of the company, calls which used to be taken by higher-paid
secretaries administrative assistants in each individual department.
A second, more recent use of the term "insourcing," is the practice of taking jobs that normally are, or previously were, "outsourced" to a foreign country, and contracting them to other companies within the same country, for the purposes of better quality control, faster response times, becoming eligible for government subsidies/incentives tied to keeping jobs "at home," etc.
Sticking with the example of a call center, in recent years there has been a trend of outsourcing call centers to other countries, particularly India, but for various reasons some American companies have started "insourcing" their call centers to rural parts of America, where wages are still relatively low, but for certain purposes quality of service can be higher, and government incentives can be lucrative.
In both of these cases, "insourcing" is the opposite of outsourcing, whether it be outsourcing work to another company in the first usage, or outsourcing work to another nation in the second.