反面（はんめん）, a noun meaning 'the opposing side', is a construction in Japanese that appears between two phrases, to show two contrasting or opposite features of a single person or thing. This usually translates as 'while (A), (B)', 'although (A), also (B)', 'on the other hand to (A), (B)'.
Being a noun,
反面（はんめん）, can be used after any word that could create a modified noun, such as verbs, い-Adjectives, な-Adjectives, or even other nouns followed by である.
都内（とない）に引（ひ）っ越（こ）して色々（いろいろ）と便利（べんり）になった反面（はんめん）、家賃（やちん）が前（まえ）住（す）んでいた所（ところ）の倍（ばい）になった。
While moving to Tokyo has made many things more convenient, the rent has doubled from where I used to live.
カリフォルニアの夏（なつ）は日本（にほん）より熱（あつ）い反面（はんめん）、湿度（しつど）が低（ひく）いので過（す）ごしやすいそうです。
Although summer in California is hotter than Japan, I heard that it is more comfortable because of the low humidity.
あの日本語（にほんご）教室（きょうしつ）の先生（せんせい）達（たち）は日本語（にほんご）を教（おし）えるのがとても上手（じょうず）な反面（はんめん）、生徒（せいと）達（たち）にはとても厳（きび）しいそうだ。
Although the teachers at that Japanese language school are very good at teaching Japanese, they are very strict with their students.
田中（たなか）くんはとても頭（あたま）のいい子（こ）である反面（はんめん）、怠（なま）け者（もの）なのでいつも先生（せんせい）に怒（おこ）られています。
Although Tanaka-kun is very smart, he is always getting scolded by the teacher because he is lazy.
Caution - Because
反面（はんめん）, is used to express contradictions, it will most often describe a positive and a negative, but cannot describe a positive and another positive, or a negative and another negative.
あのパティシエが作（つく）るお菓子（おかし）はとても美味（おい）しそうに見（み）える反面（はんめん）、食（た）べてみると味（あじ）はいまいちだそうだ。
While the pastries made by that pastry chef look very tasty, the taste is not so good when you try them.
あのパティシエが作（つく）るお菓子（かし）はとても美味（おい）しそうに見（み）える反面（はんめん）、とても美味（おい）しいそうだ。
While the pastries made by that pastry chef look very tasty, apparently, they taste very good.