Episodic Content is content that Lord of the Rings Online releases in periodic updates.
The Ballad of Bingo Boffin
The first of such Episodic Content was released in 2015 and is still available now to be played is 'The Ballad of Bingo Boffin'. It allows you to follow the trail of 'Bingo Boffin' as he traverses Middle-earth seeking fortune and adventure. He also reappears during a number of the festivals as part of other quests.
The Lay of Rust and Rime
The Lay of Rust and Rime is a series of episodic content taking place soon after the storyline of Eryn Lasgalen and the Dale-lands. The first episode was released on March 14, 2018. The second half began on June 6, 2018. You need to have completed as far as "The Darkness Remains" on the "A Darkness in Ruin" quest line to unlock the Lay of Rust & Rime. The pre-requisites for unlocking The Lay of Rust & Rime are completing The Trail of Rust and the first five quests in the "A Darkness in Ruin" quest line.