Throughout Sacred Scripture, we are told to "seek the face" of the Lord, which means that we are told to always strive to be in His presence.
Because God became man, in the person of Jesus Christ, we know that He had a real, human face. Thanks to the presence of some carefully preserved materials, we are able to have a sense of what that face actually looked like, even 2000 years after the fact.
The Images
While Jesus walked the Way of the Cross, carrying His own cross to Calvary to be crucified, Scripture tells us that He stopped and fell several times. During one of these painful moments, a young woman, (tradition names her Veronica) came forward to wipe the face of Jesus with a cloth. The blood of His face stained the cloth, leaving an image behind. This is referred to as Veronica's veil.
When He was buried after His passion and death, the body of Jesus was wrapped in a cloth shroud, as was the custom at the time. This included an additional cloth that was wrapped around His face. Due to the depth of His wounds, the blood of Jesus stained this cloth, leaving an image behind, both on the shroud and on the cloth. Many tests and studies have been done on each of these items, and an image of the Face of Jesus has been extracted from them.
There has never been a shortage of people claiming both that these items are authentic / fake, but the devotion to them has been steadfast for centuries. Remarkably, in the early 1900s, a young polish religious sister, St. Faustina Kowalska, had a vision of Jesus appearing to her with a message about His divine mercy. St. Faustina had a painting commissioned of this image of Jesus by a non-Christian painter who was famous at the time. The image of Jesus she saw matches the image extracted from the shroud of Jesus almost exactly, although the painter had never seen it. 
On April 16th, 2019, St. Mary's of Bellevue was consecrated to the Holy Face of Jesus Christ. We prepared for this special event with a Novena (9-day prayer), which is linked here.