I thought there was almost no difference, but to be exact, there is.
In kanji, it may be easier to understand the gap.
a fighting man or a serving man
bushi: 武士
武 (bu) means ” a fighter with a weapon “
士 (shi) means ” a man “
So in a strict sence, bushi means ” a fighting man with a weapon “
samurai: 侍
侍 means “one who serves.” Samurai served to a noble or a imperial family.
People (including Japanese) tend to call a man with katana swords ” samurai”.
But it would be more accurate if we call him ” bushi “.
Even japanese people are not aware of these difinitions, so nobody points out which word you should use.
