The term sequence in a poker context simply refers to the ordering of the cards. When we hold cards of direct consecutive rank i.e. 5,6,7,8,9 we can refer to them as being in sequential order

The term sequence is not specific to poker and essentially refers to a set of items in a specific order. 

In this guide we’ll learn the following - 

What is the Sequence of Cards in Poker?

The lowest card is a deuce (two) all the way up to ten. We then have the ‘broadway’ cards, Jack, Queen, King and then Ace being the highest. Note that Aces can serve as the highest card at the top of the sequence or it can serve as the lowest card at the bottom of the sequence (one lower than the deuce). Whether Ace is high or low depends on context and sometimes the specific poker game in question. 

How Many Cards in Sequence Make a Poker Straight?

It does depend on the poker variant being played, but the majority of poker variants make a straight using 5 cards in sequential order i.e 5,6,7,8. Four cards in sequential order doesn’t make anything at all in most poker variants, although it does mean that if we pick up the right fifth card we can make the straight. 

What is a Rundown in PLO?

A rundown in PLO is where we are dealt four preflop cards in sequence order, for example T987 is known as a ten high rundown. The starting hand can still be referred to as a rundown even if there are gaps in the sequence. For example, T876 is referred to as a ten high rundown top gap

What is a Suited Connector in Hold’em?

A suited connector in Hold’em is where we are dealt two cards in sequence order (and they are also suited). For example, 7d8d (seven eight of diamonds) is a type of suited connector. When there is a gap in the sequence, for example 7d9d it is referred to as a suited gapper

Summary

The term sequence refers to the ordering of the cards. The word is not specific to poker and is a standard English term used to describe the ordering of items.