The Piano Sonata No. 19 in G minor, Op. 49, No. 1, and Piano Sonata No. 20 in G major, Op. 49, No. 2, are short and relatively simple sonatas by Ludwig van Beethoven, published in 1805 (although the works were likely composed several years earlier). These sonatas are referred to as the Leichte Sonaten ("Easy Sonatas") and were most likely composed by Beethoven as teaching pieces meant to be passed around to his friends and students. It is said that these pieces were accidentally published by his accountant during a period of financial distress.

The Piano Sonata No. 20 was probably written around the time Beethoven composed the Third and Fourth sonatas, but because it was published in Vienna in 1805, nearly a decade after it was written, it was assigned then-current opus and sonata numbers, placing it amid works from the composer's middle period. Similar circumstances caused Beethoven's B flat Piano Concerto to appear as his Second, even though it predated the First. Owing to his perfectionist tendencies, Beethoven often suppressed works in his early years, either revising them later for publication, or determining after reflection that they in fact did meet his high standards. Still, he withheld many early works from publication for life, apparently never satisfied with them. In the case of this sonata and its immediate predecessor (No. 19), it was Caspar van Beethoven, the composer's brother, who decided they were worthy of publication. Against the composer's will, he presented them to a publishing house, thus allowing posterity to hear works that might otherwise have gotten lost or destroyed. It is believed that, had Beethoven himself released this sonata for publication, he would have called it a sonatina, owing to its modest proportions.

Source: Wikipedia