This is the 220th most frequent Chinese word.
建
"建" means "to build" or "to establish."
In this sentence, '建' is used to mean 'to build' or 'to construct' a physical structure.
他们计划在这里建一座新的图书馆。
They plan to build a new library here.
Here, '建' is used as part of '建于', indicating the establishment or founding of an organization.
这个公司建于1995年，有很长的历史。
This company was established in 1995 and has a long history.
In this context, '建' is used figuratively to mean 'construct' or 'develop' an abstract concept like a solution.