A fencer is a person who does fencing: the sport where two people “fight” with long, thin swords. They are not trying to hurt each other for real.

A fencer擊劍選手 is是 a person who does fencing從事擊劍運動的人 the sport where two people一種兩個人 with long, thin swords用又長又細的劍 "fight"「打鬥」的運動。 They他們 are not trying並不是想 to hurt each other傷害對方 for real真的

They wear a mask and a thick jacket, and they score points by touching the other person with the sword.

They他們 wear戴 a mask面罩 and和 a thick jacket厚外套 and they score points而且 by touching the other person with the sword用劍碰到對方就能得分

It is a school sport and an Olympic sport. The swords have special names (foil, épée, sabre), but the person is still a fencer in all of them.

It它 is是 a school sport一項學校運動 and也是 an Olympic sport奧運項目。 The swords have special names這些劍有特別的名稱 (foil, épée, sabre)（foil、épée、sabre） but但 in all of them不管用哪一種 the person is still a fencer這個人都叫fencer

The word is everyday sports English, not slang and not especially formal.

The word這個詞 is是 everyday sports English日常的運動英語 not不是 slang俚語 and也不算 not especially formal特別正式

Though actually, the first picture many learners get is wrong: this is not a person who builds a garden fence. That is a different “fence”. A fencer is the athlete.

Though actually不過其實 the first picture many learners get很多學習者一開始想到的畫面 is wrong是錯的: this is not a person who builds a garden fence這不是指蓋花園圍籬的人。 That那 is是 a different "fence"另一個「fence」。 A fencerfencer is指的是 the athlete這項運動的選手