Masjid Aisha, located in the area of Taneem approximately 7 km northwest of মসজিদুল হারাম, is the nearest Miqat point outside the Haram boundary (Hil). It is named after Aisha (may Allah be pleased with her), who was instructed by নবী করীম (সাল্লাল্লাহু আলাইহি ওয়া সাল্লাম) through her brother Abdur-Rahman to go to Taneem to enter ইহরাম for her উমরাহ during the Farewell হজ্জ.
You need to go to Taneem if you are already inside মক্কা মুকাররমা (within the Haram boundary) and wish to perform a new উমরাহ. Since ইহরাম for উমরাহ must be entered from outside the Haram boundary, you cannot simply make the intention from your hotel in মক্কা মুকাররমা. Taneem/Masjid Aisha is the closest and most convenient exit point for this purpose. Other options include going to Ja'ranah or Hudaybiyah, but Taneem is by far the most popular due to proximity.
The মসজিদ has modern facilities including: ablution areas, সালাত spaces, separate sections for men and women to change into ইহরাম garments, and shops selling ইহরাম cloths and supplies. Taxis from the Haram area to Masjid Aisha are readily available — the trip takes about 15-20 minutes. Many হজ্জ/উমরাহ operators arrange group transport to Taneem for those wishing to perform a second উমরাহ. Upon arriving at Taneem, perform গোসল if possible, change into ইহরাম, make your niyyah for উমরাহ, begin the তালবিয়াহ, and return to the Haram for তাওয়াফ and সাঈ.