Before leaving the Moon on Apollo 11, Neil Armstrong's final task was to remind Buzz Aldrin to place a small package of memorial items to honor the international astronauts, Komarov, Yuri Gagarin, and the Apollo 1 astronauts Virgil Grissom, Edward White, and Roger Chaffee.

This was left on the landing stage of the Eagle, the Lunar Landing Module.

This plaque represents those astronauts and cosmonauts who died in the quest to reach outer space and the Moon.

More Info: en.wikipedia.org