In the church government and polity documents (as well as the myriad of meta discussion on the internet) for various Protestant traditions it is common to find either the term "Elder led" or "Elder ruled". What is the difference between these two terms?
The most significant difference is in how new Elders come into office.
In an Elder Ruled church, existing ordained elders have the responsibility of finding or training equipped leadership and appointing them to office in the local church.
In an Elder Led church, the appointed Elder board may exercise spiritual oversight over the body but ultimately also serves at the pleasure of that body. The current Eldership may bring a recommendation for new appointments, but it is the congregations responsibility to elect them to the board.
The latter concept is actually a variant on congregationalism, in which the final say in major matters (e.g calling a pastor, changing the budget) is put in the hands of the whole church by means of a vote, usually having heard a recommendation from the Elders. On the other hand the Elder board is given authority to handle smaller issues without consulting the congregation. Examples of Elder Led Congregationalism are most "community" churches, many Evangelical churches (including most of the EFCA).
On the other hand Elder Rule tends to be found in in traditions with more ecclesiastical structure, especially Presbyterianism and most Reformed churches.
Bonus: Notably for being absent from my examples above is the Baptist tradition. While "traditionally" most Baptist denominations employ some form of Elder Led Congregationalism, there is also a wide enough variety in what this means and how it is implemented to make them hard to broadly categorize. In recent history, many churches with otherwise baptist doctrine have adopted a much less congregationalist and much more Elder Rule system.