Destiny 2's Eververse store refreshes about every three months when a season ends, allowing players to purchase new cosmetics and emotes. The last reset added the Temporal Surge feature, allowing the sale of otherwise unavailable old emotes
Temporal Surge will differ from other regular Eververse purchases in several aspects. The first difference is that the Surge will add older, no longer available items, originally contained in Bright Engrams.
Each Temporal Surge will apparently have a different theme, with the current one putting focus on Year One emotes. As previously mentioned, Temporal Surge will happen in a limited time window each time. This particular one started on 06 November 2018 and will end on 13 November 2018.
Another example, and perhaps the most important one is that players will only be able to purchase the emotes only with Silver, the paid currency in Destiny 2. Players can normally use Bright Dust to purchase Eververse items, but since this will not be the case with Temporal Surges, they will have to pay for emotes with real life currency, should they decide to complete their emote collections.
While this course of action is definitely not consumer-friendly, at least the emotes will be purchased directly and not contained in loot boxes. There will be different pricing on each of the three emote rarities. Rare emotes will cost 200 Silver, Legendary emotes will go for 500 Silver while Exotic ones will cost 1.000 Silver.
For reference, 500 silver costs $4,99 / €4,99 / ~£4,35 which also happens to be the cost of a single Legendary emote. There are discounts on bulk purchases of Silver so the emotes can turn out to be slightly cheaper, but these prices are usually taken as the basis.
This can turn into a proper nightmare for some fans, as customer mishandling has happened before and Bungie weren't exactly transparent about it. You can read the official blog post announcing Temporal Surges here.