*歌（うた）”music with lyrics”
→Both 歌 (うた) and 曲 (きょく) refer to music, but 歌 (うた) generally refers only to songs with lyrics.
→Although it originally means a solo singer who has been working alone from the beginning, it is often used when a person who was originally performing in a group of two or more performs music on his/her own.
→When it is two people, it is often called デュオ (でゅお “duo”).
→アイドル (あいどる) means Japanese or Korean pop stars, especially those whose main appeal is their cuteness or coolness in appearance.
→It can refer to a favorite solo singer but is often used to refer to a favorite member of an idol group.
→First press limited editions of Japanese CDs often include bonus tracks and bonus videos. Posters and stickers are also sometimes included.
*オリコン…[number]位（おりこん…い）”Oricon Chart #…”
→Oricon Chart is like Billboard Chart. When we say 「オリコン…位」, in most cases, we refer to the ranking of CD sales.